Telephone-transmitter



(No Model.)

H. GOTTRELL.

TELEPHONE TRANSMITTER.

No. 518,916. Patented Apr. 24, 1894. v

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UNITED STAT S HERBERT COTTRELL, OF

PATIENT @EErcE.

NEWARK, NEW JERSEY.

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 518,916, dated April24, 1894.

Application filed March 15, 1894.

To all whom it may concern.-

Be it known that I, HERBERT Oo'rTRELL, a citizen of the United States ofAmerica, residing in the city of Newark, county of Essex, and State ofNew Jersey, have invented certain new and useful Improvements inTelephone-Transmitters, of which the following is a specification. V

My invention consists in producing a novel resistance piece fortelephonic transmitters, its most important feature being that it is soconstructed that there is an unbroken connection through it in allconditions of the instrument, and a second connection parallel with thefirst, which latter is opened and closed or varied in resistance byvibrations of the diaphragm of the transmitter. I preferably arrange thetwo connections on one common piece. To do this I provide a suitablestrip or rod of some conducting material, as a thin strip of carbon orof some carbonized substance, from which project knobs or points thatare but lightly if at all in contact with each other when the strip isstraight, and are brought more or less intimately in contact through theoperation of the diaphragm. These projecting points or knobs on thestrip may be brought together byflexure of the strip or maybe crowdedtogether by being pushed against the walls of a cone which fits over thepoints or knobs and cams them together. The fiexure may be produced bypushing and pulling on a knob or point or on the rod or strip; andinstead of flexure which operates to bow a flat strip the operation maybe to twist a rod, around the periph: cry of which knobs or projectionsof suitable shape are arranged, preferably in a sort of spiral. Thislatter I call my torsional form. As to the material, I may use anysuitable substance of large electrical resistance, carbon or somepreparation of carbon being preferable; as, for example, manila papercarbonized by the process used to prepare the filament of the familiarincandescent lamp. The whole constitutes a resistance piece of which therod or strip is the base and the knobs or points are the projections.There is nothing novel in the manner of connecting this resistance inthe telephonic circuit. The novelty lies in the resistance piece itself,as

already stated. The telephonic circuit may Serial No. 503,707. (Nomodel.)

,is a modification of the device of Fig. 1, in

which-the diaphragm is connected with the strip of the resistance pieceby a string or wire. Fig. 4 is a side View of a modification in whichthe camming cone is used. This cone is attached to the diaphragm. Figs.5 and 6 are'end and side views respectively, of the torsional form oftransmitter.

Referring now particularly to Fig. 1, there is shown back of the mouthpiece 1 a corrugated diaphragm 2, from the back of which projects.inwardly a rod 3 which presses upon one of the knobs of the resistance.These knobs 4 are all arranged side by side along the front of theflexible and somewhat elastic strip 5, which is integral with them.These knobs and the strip form together the resistance piece. Theresistance piece is shown supported at its ends by two springs(iattached to screws 7 which are fastened to a block 8 of insulatingmaterial. This block is shown as attached to a spring 9, which bearsatits ends against the posts 10.a nd is pressed at its middle pointbythe endof a through the wires 12 which are in electrical contact withthe screws that support the resistance piece.

In Fig. 3 the mouth piece is omitted. The diaphragm 2 is connected withthe strip 5 by ICO a rod 3 which is firmly attached to both thediaphragm and the strip. The other parts are as in Fig.1. The onlydifference between the arrangement of Fig. 1 and of Fig. 3 is that theposition of the resistance piece is reversed from right to left and therod 3 is attached to the back of the base of the resistance piece. Butif the set screw 11 is screwed farther in in the arrangement of Fig. 3,it tends to separate the knobs of the resistance piece, whereas in Fig.1, this movement of the set screw tends to bring the knobs together.

Fig. 4 shows the parts arranged substantially as in Fig. 3, except thatthe spring 9 is thrown on to the other side of the posts 10 and thescrew 11 is shown as penetrating somewhat into the body of the block 8.The screw is of course a draw screw in this form. It is shown in thisform to illustrate the fact that either a push screw ora draw screw canbe used for any one of the arrangements shown. The resistance piece issomewhat different in Fig. at from that of Figs. 1 or 3, the projectionsbeing shown as rods 4: which do not stand out at right angles from theflexible strip of the resistance piece, but converge toward each otherfrom the strip outward. The diaphragm 2 has a cone shaped cap 13attached on its rear side which fits over these points, and when movedin or out by the sound waves striking the diaphragm varies the contactin degree between these points.

In Figs. 5 and 6 the diaphragm 2 is shown as connected bya rod 3 with anarm 14, which extends at right angles from the thin rod 15, which isattached at itslower end in the bearing 16, and is supported also in abearing 17 at its upperend, in which, however, itis free to turn.Arranged along the length of the rod 15 are projections 4" having flatheads, the projections and heads looking not unlike 0rdinary fiat headedtacks. These are not essentially unlike the knobs 4 or projections 4.The heads overlap each other and are nearly or actually in contact, andwhen the diaphragm is pushed in or pulled out the contact between theseheads is established orincreased on the one hand, or broken ordiminished on the other, thereby varying the resistance between thewires 12. As will be seen from the inspection of any one of thesefigures, no movement of the diaphragm can possibly rupture the circuit,since that is always complete through the base of the resistance piece,along which the variable-contact shunting projections are arranged.Obviously, the resistance will be greatest when the circuit is completedonly through the base of the resistance piece. For, if the projectionsare brought in contact there is then established, in addition to thecircuit through the base, a circuit through the two contactingprojections, which shunts that portion of the strip or rod that liesbetween the points at which these projections join the base. Taking, forinstance, Fig. 1, on which are shown seven projecting knobs, there aresix spaces between pairs of adjacent knobs. These sections of the stripare all shunted through the knobs if all the knobs are in contact, eachsection being shunted through one pair of contacting knobs. The samestatement is true of the arrangements shown in Fig. 3 and of that ofFigs. 4. and 6. The resistance of the projections is preferablyconsiderably smaller than the resistance of the base along which theyare set.

It is very important, particularly in long distance telephony, that theline should never be broken, no matter how violent may be the vibrationof the diaphragm. This point of advantage I secure as above explained,since I do not use separate electrodes held in contact with each other,the pressure between which is varied by movements of the diaphragm. Thentoo, the fact that there are a number of points in contact is ofadvantage, because, even though the sound may be violent enough to throwtwo or more of them out of contact, it still may not throw all of themout of contact. Doubtless the mere flexure or twisting of the base ofthe resistance piece itself produces some variation in its resistance,and consequently, in the resistance of the circuit. But it is the effectof shunting the sections of the base that I- rely upon.

The receiver may be any telephonic receiver adapted for use in a circuitwith a variable resistance transmitter.

Without limiting myself to the precise details shown, what 1 claim, anddesire to secure by Letters Patent of the United States, is-

1. In a telephone transmitter, a variable resistance piece, consistingof a conducting base having projections extending therefrom, adiaphragmsusceptible of being vibrated by sound waves, and means for varying thecontact between the projections, in correspondence with the vibrationsof the diaphragm, to produce variations in the current, substantially asdescribed.

2. In a telephone transmitter, a variable resistance piece, consistingof a conducting base and projections extending therefrom, a diaphragmsusceptible of being vibrated by sound waves, and means for varying thecontact between the projections by communicating the vibrations of thediaphragm to the base of the resistance piece, to produce variations inthe current, substantially as described.

HERBERT COTTRELL.

In presence of- THOMAS EWING, J r., CHAS. F. BIsHoP.

